With rapid spread of information-related instruments, communication instruments and others such as personal computers, video cameras, cell phones and the like in recent years, development of batteries that are utilized as power sources for them is considered to be important. Among such batteries, lithium batteries are specifically noted from the viewpoint of realizing a high energy density.
Lithium batteries that are now on market use an electrolytic solution containing a combustible organic solvent, and therefore it is necessary to fit a safety device for preventing temperature elevation in short circuit and to make improvement in point of configurations and materials for prevention of short circuit. As opposed to this, a lithium battery in which the electrolytic solution is changed to a solid electrolyte layer so that the battery is solid as a whole is considered to be excellent in production cost reduction and productivity since a combustible organic solvent is not used in the battery and the safety device to be therein can be simplified.
As a solid electrolyte for use in such a solid electrolyte layer, for example, there are known sulfide solid electrolytes to be produced using lithium sulfide, diphosphorus pentasulfide, lithium iodide and lithium bromide as starting materials (for example, PTL 1).
As a method for producing the sulfide solid electrolyte using lithium sulfide, diphosphorus pentasulfide and others as starting materials, for example, a method of using a hydrocarbon solvent is proposed in PTLs 2 and 3.
In PTL 4, there is disclosed a method of preventing adhesion and granulation of a sulfide solid electrolyte before formation of fine particles by grinding mixture of a sulfide solid electrolyte that contains a sulfide and one or more halides, an ether compound and a solvent.
On the other hand, in a production method for a sulfide solid electrolyte using an organic solvent, it is known that the organic solvent having remained, if any, in the resultant sulfide solid electrolyte may cause reduction in Li ionic conductivity and therefore such a residual solvent must be reduced (for example, PTL 5).